Organic nitrogen mineralisation in two contrasting agro-ecosystems is unchanged by biochar addition

Biochar additions to soil have been reported to enhance soil fertility whilst simultaneously storing carbon (C). We tested whether either fresh or field-conditioned (aged) biochar amendment to two contrasting agricultural soils would alter the mineralisation of organic N compounds. The mineralisation of 14C-labelled amino acids and peptides were determined over 20 days within each soil. An exponential kinetic decay model was subsequently fitted to the mineralisation data. Overall, statistical analysis revealed significant but small differences between the two biochar treatments and the unamended control treatment. We conclude that biochar has very limited impact on the mineralisation rate of low molecular weight dissolved organic N compounds in these agro-ecosystems. ► Biochar addition has limited impact on low molecular weight DON mineralisation. ► Limited change in mineralisation was seen for two contrasting agricultural soils (from Western Australia and Wales). ► This very minor impact was seen for the first few years after application.